On this day, he hopes to prove the car’s mettle by driving it from his WaterCar headquarters in nearby Fountain Valley, Calif., to Catalina Island, 30 miles offshore.

The only problem is he has never tested the car on open water.

March has been building and testing amphibious cars, or amphibians, for years. He filed patents for his first amphibian in 2003. Six years later, he set the Guinness World Record for fastest amphibious car with the Python, which has a 450-horsepower Corvette engine and can hit 60 mph on the water.

The car that March is test-driving to Catalina is the Panther, a smaller, off-road amphibian — that can go 45 mph on water and 85 mph on land — that is the entrepreneurial fruit of 12 years of trial and error and hundreds of thousands of dollars in research and development.

Ever since he posted a video online of the Panther in action, March’s phone hasn’t stopped ringing. The car already has been filmed in three reality TV shows, including an episode of the current season of “The Bachelor.”

He also has received a deluge of emails from buyers around the world.

The embassy of the United Arab Emirates has ordered one, and Sheik Hamdan bin Mohammed Al Maktoum, the crown Prince of Dubai, has ordered six.

“I’ve got guys that are throwing money at me,” March said. “It’s a fun position to be in.”

Back in Newport Harbor, March points his Panther toward the horizon. He’s surrounded by three powerboats, which are carrying friends, family and a case of Champagne.

He steps on the gas, and the Panther slowly rises up out of the water. As March moves into deeper water, dolphins leap up around him. The shore disappears from view, and a whale comes up for air.

“It’s running nice,” March’s voice comes in over the radio. “If it weren’t for the swells, I’d kick it up a notch.”

“We’re at 13.5 miles,” March’s partner, Fred Selby, radios from his boat before the halfway mark. “This is the point of no return.”

March is particularly well-positioned to build a successful amphibian. He owns Fountain Valley BodyWorks, an auto-repair shop that fixes 500 to 600 cars a month. He also is an avid boater.

March’s goal was simple: Build a car that could drive on the freeway but also keep up with a boat on the water.

WaterCar has gotten around manufacturing regulations because the company sells the car as a kit. Buyers purchase the body but must pay a third party to install the engine, which, on paper, means the buyer — not WaterCar — built the vehicle. The owner then must register it as a boat and as a car.

Like so many great ideas, March’s first water car was born in his basement, which he flooded to see whether his prototype would float. But the real challenge wasn’t waterproofing. It was getting the car up and out of the water when he pressed the gas.

“Anyone can build a car that floats,” March said. “It’s a lot harder getting it on a plane.”

March’s first prototype in 2003 looked like a small Camaro. When it was switched to boat mode, the tires retracted and hydraulic metal plates covered the wheel wells. March posted a video of it online, and the clip went viral.

WaterCar’s first customer, an electronics manufacturer from Pennsylvania named Peter McIlroy, is scheduled to receive his Panther sometime in February.

McIlroy, who test-drove the Panther, said it is “head and shoulders above” anything he has ridden.

Catalina Island was a foggy blur when March idled into the harbor.

An hour and 10 minutes after leaving Newport Harbor, March stood at the back of his yacht in Avalon Bay and popped a Champagne cork into the water.

“I never thought we’d make it the first time out,” March said.

March wanted to drive the Panther into town. But the tide had complicated a land approach. The Panther is designed for paved loading docks and relatively smooth shores, not the steep, rock-strewn banks of Catalina at low tide.

“It loves a sandy beach,” March said. “(But) I’m out here to learn what I can.”

March drove onto shore. But the grade was too steep, and March was forced to reverse the jets, which sent a barrage of small rocks up into the underbelly of the car. It wasn’t until later that he realized a wheel fastener had been damaged. March was visibly upset but glad he found a weak link. He said he plans to replace the snapped part with an aircraft-grade version that is much stronger.

“Each time you break something, you learn something,” March said. “That’s what it’s all about.